This invention relates generally to magnetic recording systems for digital information, and more specifically to such a system capable of driving a magnetic transducer with a current higher than that due only to a power supply of a given voltage, in order to make possible the recording of high frequency digital signals.
Magnetic transducers are inductive, so that they offer high impedances when recording high frequency digital information. Correspondingly high drive voltages are therefore required. It might be contemplated to provide inductance capacitance resonance networks in order to obtain sufficiently high voltages. This solution is unsatisfactory because it would be difficult to maintain LC resonance in cases where the information being recorded varies in a wide range of frequencies.
Another solution is found in an article entitled "Overwriting Technologies of Magneto-optical Disks by Magnetic Field Modulation Method" in pp. 63-70 of the Vol. 14, No. 17, issue of Television Gakkai Technical Reports published February 1990 by Television Gakkai of Japan. This article teaches the connection of two inductive reactors between magnetic transducer and power supply. Two switches are alternately turned on and off to cause the transducer to be excited from the power supply via one of the reactors and then the other. Energy is stored on one of the reactors when the transducer is being excited via the other reactor. Accordingly, when the transducer is subsequently excited via said one reactor, the energy that has been stored thereon is also utilized to energize the transducer. A net current flowing through the transducer is therefore of greater magnitude than the current offered solely by the power supply.
This prior art transducer drive system is objectionable for several reasons. First, it requires two reactors, making the system bulky and expensive. Second, constant current flow through the two reactors involves considerable power loss because of their resistivity. Third and finally, as the current flows through each switch after flowing through both reactors, power loss also occurs at the two switches.